1. Field of the Invention
The present invention generally relates to an apparatus and method for cutting target material. The present invention more particularly relates to an apparatus and method for cutting target material of a substantial thickness using a thermite based charge.
2. Description of the Related Art
A number of devices for cutting materials of a substantial thickness are known in the art. Many of these devices employ explosive shaped charges which deliver energy to the surface of a material in the form of a high pressure, high velocity shock front. The conical or xe2x80x9cVxe2x80x9d shaped charge, for example, explodes and focuses cutting energy onto the surface of the material to be cut. A primary disadvantage of explosive shaped charges is that they generate excessive noise and debris upon detonation. This noise and debris can pose potentially serious health and safety hazards to someone using a cutting device which employs conventional shaped charge explosives.
U.S. Pat. No. 2,587,243 discloses an apparatus for producing a gaseous penetrating jet for cutting materials or objects. This patent uses a chemical charge which, when detonated, ruptures a means interposed along the path of the generated high velocity gases. The means converges upon rupture and causes a material placed beneath the apparatus to be cut by the resultant high velocity gas explosion.
U.S. Pat. No. 4,693,181 discloses a linear cutting charge device including an explosive mass formed in the shape of a bar. Detonation of the charge in this patent is disclosed as stating that it compresses a metal liner and converts the metal liner into an outwardly projected slug of metal, the shape of which is dependent upon the shape of a cavity of the device. It is this outwardly projected slug which penetrates the work surface of a material which is cut or deformed by the detonation and subsequent penetration.
U.S. Pat. No. 4,815,384 discloses a device with a housing for use with joinable or interconnectable cutting charges. The stated purpose of this patent is to avoid formation of a saw-tooth cutting profile on a target work surface acted upon by the device discussed in the patent.
Thermite-based cutting devices which employ a cutting flame produce virtually no extended shock wave and generate relatively little over pressure. Thermite-based cutting devices do not present the same health and safety hazards which are attendant upon explosive shape charge cutting devices.
What has not been disclosed in the prior art, however, is use of a thermite-based apparatus for directing or focusing a cutting flame derived from the activation of a thermite charge for the purpose of effectively focusing the cutting flame across a desired cutting location on an elongated, round or possibly rectangular workpiece, and for providing relief for reaction products, thereby preventing back pressure around the nozzle.
In spite of the foregoing known apparatus and methods for cutting material, there remains a real and substantial need for an apparatus for cutting material which employs a thermite-based charge to ensure a safe and efficient cutting action.
The present invention is an improved nozzle for thermite-based cutting torches. A typical thermite cutting torch utilizing the present invention will include a housing having an inner cavity, and securing the nozzle of the present invention. An energetic material, for example, a thermite charge, is contained within the housing""s inner cavity to provide the torch with a source of cutting flame. An activating device, such as an igniter, is coupled to the thermite charge.
The nozzle of the present invention includes an elongated aperture, thereby providing for maximum flow of cutting flame to the desired location of the cut. The nozzle face is dimensioned and configured to eliminate the need for a standoff distance between the aperture and the workpiece, by defining an arc to match the contours of the largest workpiece the torch is designed for, and a groove for eliminating backpressure and directing flow of reaction products from the nozzle. This arc will ensure that the torch is self-centering when held against the workpiece. The nozzle face also defines a groove coincident with the long axis of the nozzle when viewed from either the top (back) or bottom (face), permitting free flow of reaction products in the direction of the desired cut, and out of the cutting area once they have exited the aperture and contacted the workpiece. This free path provides for minimized backpressure within the nozzle area and optimal energy delivery to the cutting zone.
The activation means for igniting the thermite charge may be any conventionally known activation means, or alternatively may be a primer, such as is typically used to ignite the powder within a firearm cartridge. The torch may therefore be activated by striking the primer, thereby igniting the priming compound, which in turn ignites the thermite charge.
The cutting torch may be held against the work piece either by clamping it against the work piece, or by holding the cutting torch using a holder having a means for striking the activation means, for example, a trigger mechanism and firing pin as is typically used to strike the primer of a cartridge within a firearm.
It is therefore an object of the present invention to provide a nozzle for thermite cutting torches maximizing the flames directed towards the desired cut.
It is another object of the present invention to provide a nozzle for thermite cutting torches eliminating the need for a standoff distance between the nozzle and the workpiece.
It is a further object of the present invention to provide a nozzle for thermite torches providing for centering of the nozzle aperture over the desired cut.
It is another object of the present invention to provide a nozzle for thermite cutting torches having a groove for providing a free path for reaction products, thereby minimizing backpressure within the nozzle region.
It is a further object of the present invention to provide a thermite cutting torch that may be used by clamping it against the work piece.
It is another object of the present invention to provide a thermite cutting torch that may be held against the work piece by a torch holder having means for striking the activation device within the torch.
These and other objects of the invention will become apparent through the following description and drawings.